The development of virtual routers within a single network element provided certain benefits and functionality unavailable with legacy routers. For example, a single network element with virtual routers could service multiple Internet Service Providers and/or corporations with the single network element.
FIG. 1 (Prior Art) is a diagram of a single network element with virtual routers. In FIG. 1, a network element 101 includes virtual routers VR-A 111, VR-B 113, and VR-C 115. Each of the virtual routers 111, 113, and 115 respectively receive traffic from ingress ports 103A-103C and respectively transmit traffic out of the egress ports 151A-151C as illustrated in FIG. 1. The virtual router VR-A 111 receives traffic 109A from the ingress port 103A and transmits the traffic 109A out of the egress port 151A. The virtual router VR-B 113 receives traffic 109B from the ingress port 103B and transmits the traffic 109B out of the egress port 151B. The virtual router VR-C 115 receives traffic 109C from the ingress port 103C and transmits the traffic 109C out of the egress port 151C.
Network elements that support virtual routers, performed inter-VR forwarding based on the forwarding scheme described (i.e., with standard interfaces). If VR-A 111 received a packet for transmission to VR-B 113, then the VR-A 111 looked up the next hop in its routing table, found an interface that was associated with the ingress port 103B, and forwarded the packet based on that interface.
Despite the advantages offered by virtual routers and the capability of a single network element to behave as multiple routers, the virtual routers within a single network element do not communicate routing and/or forwarding information as if separate routers.